In plumbing vernacular, graywater is wastewater from bathtubs, shower drains, sinks, washing machines and dishwashers, accounting for about 50 to 80 percent of the outflow produced in homes. (Some jurisdictions, however, exclude water from the kitchen sink or dishwasher, classifying such water as dark graywater or black water.) In commercial buildings or facilities such as schools, graywater mostly comes from sinks and shower drains, possibly dishwashers.
Domestic wastewater is usually combined at the sewer. Sewage water is chemically treated to limit pollution and health risks before being returned to the environment; most graywater ends up as effluent in rivers and oceans.
When separated, because it contains little or no pathogens and 90 percent less nitrogen than black water (flushed from toilets/urinals), graywater does not require the same treatment process to neutralize it.
Designing a plumbing system to separate graywater from black water allows graywater to be reused for irrigation, toilet flushing and exterior washing. This requires additional space for a holding tank or a series of filters. The NAHB Research Center’s ToolBase Services says costs for the house drain pipe of a graywater system are minimal if the system is installed with the potable water rough-in while a building is under construction.
The distribution or drain pipe for graywater systems generally is colored purple. To further distinguish it from potable water pipe, purple pipe also is marked as nonpotable or reclaimed water. But total cost of a reclaimed water system depends on the site and the type of system installed.
“A graywater system could add up to 20 percent to the cost of the plumbing system. We are installing a system in a school that uses a 20,000-gallon underground tank where stormwater is collected,” says Bruce Rettig of Merit Mechanical (Newark, Del.). Charlotte Pipe’s ReUze CPVC piping is specified for this school project. “The stormwater is pumped into a mechanical room, filtered and then distributed throughout the school with another set of pumps. So there are more costs to consider beyond installing the distribution pipe and the associated labor.”
Costs for a retrofit system, however, could be much higher since a plumber would have to reconfigure the drainage system, explains Randy Knapp, plumbing products manager at Uponor who works on the plumbing applications of PEX tubing, including Uponor’s AquaPEX Reclaimed Water Tubing. This could entail ripping up floors or tearing into walls. Because it is more labor-intensive, it is a more expensive approach.
A gut remodel, on the other hand, would be a more cost-effective retrofit approach since the plumbing system would be exposed, adds Steve Clark, president of Aquatherm, which manufactures Lilac reclaimed water pipe. It’s also an effective approach if water restrictions in the local area were such that it made more sense to install the graywater system than pay higher water bills.
Water Conservation At Camp PendletonAt Marine Corps Base Camp Pendleton, one of the largest bases in the United States at 200 square miles (125,00 acres) in Southern California, about 15 BEQs (Bachelor Enlisted Quarters) are being constructed with recycled water systems using Aquatherm’s Lilac pipe. Each BEQ has about 200 rooms, equating to about 3,000 toilets total, says Donna Schipper, CEM, a cross-connection specialist (certified by the American Water Works Association) and engineering tech in the Naval Facilities Engineering Command SW stationed at Camp Pendleton.
Installation of recycled water piping on base is extensive, she says, including irrigation systems across the base and two headquarters buildings using copper pipe for recycled water. The purpose of installing these systems is to conserve potable water on the base; depending on normal usage, it is estimated that each BEQ will save 1 million gallons of water a year.
Another reason for the recycled water systems is to provide an alternative to the base’s wastewater disposal. Wastewater comes from the treatment stream of the base’s wastewater plant, which is sent to an Oceanside outfall.
“For flushing toilets, we’ll be using recycled water instead of treated drinking water and sending less wastewater to the outfall,” Schipper explains.
Her biggest challenge was coordinating inspections of the recycled water systems with state and local regulators to lessen the impact on construction schedules, as the environmental health and public health departments have oversight over Camp Pendleton’s use of recycled water. Schipper works closely with these agencies to conduct daily construction inspections; final inspections will still be conducted by state authorities.
Jesus Ortiz, plumbing/piping super-intendent at R.J. Lanthier (Escondido, Calif.), is part of the crew installing Lilac pipe at Camp Pendleton. The biggest challenge he saw on the project was how to make the installation more efficient in the field. The crew of 63 plumbers/pipefitters is still onsite to complete the final phases of the recycled water piping installation.
Code AcceptanceThe reclaimed water piping on the market today got its start in Australia as that country has been dealing with droughts for more than a decade. Severe water shortages have required the country to implement strict water-saving measures, including graywater reuse.
In the United States, several regions have undergone long periods of drought. For those jurisdictions that have adopted the International Plumbing Code, graywater can be used for sub-surface irrigation and toilet flushing. In areas that adopt the Uniform Plumbing Code, graywater can be used in underground disposal fields similar to shallow sewage disposal fields.
But the greatest push for graywater reuse or reclaimed water systems are the various green construction standards such as U.S. Green Building Council’s LEED program or NAHB’s National Green Building Code. The use of nonpotable water systems can contribute up to 10 LEED points on a project - 25 percent of the points needed to achieve a LEED-certified building.
However, it’s important for contractors and end users to know that LEED credits are not awarded for the purple piping itself, rather it is the reduction of potable water use that garners the points, explains Greg Nahrgang, new products manager at Charlotte Pipe and Foundry. “Within the LEED water efficiency credits, nonpotable water reuse is one factor,” he says. “There also are regional priority credits that allows a project extra points. About 30 percent of LEED points come out of reducing potable water consumption.”
Market GrowthGraywater or reclaimed water systems will continue to grow as the green movement grows. “In three to five years, graywater reuse systems will be standard,” Aquatherm’s Clark says. “After about 10 to 15 years, we’ll wonder why we ever flushed toilets with drinking water.”
Knapp agrees, but he sees a slow growth depending on the needs of the local area. “Dispute issues will be over water rights and how water systems are funded,” he explains. “Graywater reuse will be driven by the need to conserve water as well as the cost of water. And we certainly expect water rates to go up. I think it will take water shortages in more areas for bigger jumps in graywater installations to occur.”
Nahrgang adds: “This is a ‘not will, but when’ issue with the combination of sustained drought conditions and water restrictions on consumers. At some point, this market is going to explode. Water is going to be seen as a commodity.”